1. Field of the Invention
This invention relates to a drive belt assembly particularly used for operating snowmobiles, and it particularly relates to an improved drive belt assembly which is fatigue resistant, provides positive forward traction for the snowmobile, and substantially avoids side slippage of the snowmobile as it moves along icy or hard snow packed surfaces.
2. Discussion of the Prior Art
In snowy regions, snowmobiles are a conventional and important means of transportation. Snowmobiles are used extensively in snow regions, not only for everyday use, but they are also widely used for recreational and emergency purposes. Snowmobiles are operated on a wide variety of terrain. They are used in hilly or mountainous regions as well as on flat land. They are operated on fresh snow, on trails conditioned for snowmobile riding, on hard packed snow, on the icy surfaces of streams, rivers, and lakes, and on hard snow packed or icy roads.
Continuous drive belts are conventionally used for engaging the snow covered ground and/or icy surfaces, in order to provide the proper traction to propel the snowmobile forwardly. In order to provide the proper traction for use for the wide range of conditions in which snowmobiles are used, the design of the endless drive belt or drive track is extremely important. Generally speaking, the drive belt has a width substantially equal to the seat portion at the rear of the snowmobile, give or take a few inches. The drive belt is drivably suspended on the frame of the snowmobile and is generally positioned at the rear portion of the snowmobile, while a pair of steerable skis support the front end of the snowmobile.
One conventional snowmobile drive belt design is shown, for example, in Kell U.S. Pat. No. 3,623,780. Such drive belts are made of an elastomeric material. A plurality of transversely mounted and longitudinally spaced rigid elongated drive cleats are securely mounted on the outer surface of the drive belt. These drive cleats, which are conventionally U-shaped in cross-section, provide positive traction with the ground in order to propel the snowmobile in a forward direction. Although such a snowmobile track design is generally considered suitable for propelling the snowmobile forwardly, as the cleats bite into the snow and/or ice, the belt design, as shown in the Kell patent, has certain disadvantages.
One problem with the drive cleats which extend across the entire width of the belt is that, because of the nature of use of the snowmobile, the rigid, metallic cleats, as well as the drive belt, constantly undergo flexing between the opposite ends thereof, as the snowmobile travels across the snow covered ground while encountering rough terrain, rocky terrain, icy projections, etc. As a result of this flexing, the metal cleats fatigue at their central portions and ultimately many will break. Of course, broken cleats ultimately have to be replaced.
The problem of elongated "full width" cleats, that is, those extending across the entire width of the snowmobile, breaking, because of flexure, has been greatly alleviated by extending each cleat from one edge of the track only partially across the track, as about two-thirds across. These partial cleats extend alternately from opposite edges of the drive belt. Such a design is shown, for example, in Olson U.S. patent application Ser. No. 204,872, filed Dec. 6, 1971, entitled "Track Construction with partial Cleat" (assigned to the same assignee as this application), now abandoned.
Although the partial cleat track design does significantly alleviate the cleat fatigue and breaking problem created by the flexing of the drive cleats, such a track or cleat design has little or no effect on another significant problem with drive cleats of the type shown in the Kell patent. This problem is side slippage or "skating" of the rear of the snowmobile. Such slippage is particularly noticeable when the snowmobile is traveling across hard packed snow, icy surfaces, as on streams, rivers, or lakes, ice covered roads and the like. This side slippage is even more noticeable when the snowmobile is being turned. Such side slippage can be a safety problem if, for example, the operator of the snowmobile unexpectedly encounters icy areas or if an unusually sharp turn is required; basically, side slippage could, conceivably, cause the operator to lose full control over the snowmobile, possibly causing injury to the operator of the snowmobile, to those nearby, or to the snowmobile itself.